Although chronic nonspecific diarrhea of childhood is the most common form of chronic diarrhea without failure to thrive in young children, the etiology remains unknown. Because malabsorption of nutrients is not a factor in this disease, the cause of the diarrhea is either enhanced secretion of fluid in the distal bowel or interference with absorption of water and electrolytes from the colon. Chronic nonspecific diarrhea frequently is initiated by an acute infection, which usually is treated with a broad-spectrum antibiotic such as ampicillin, so alteration of bacterial flora in the colon may play a role in the diarrhea.

Some investigators have thought that the diarrhea might be induced by the increased intake of fluids observed in these children. However, the increased thirst is more likely to be the effect rather than the cause of the diarrhea. Some children drink large amounts of fruit juice, such as apple or grape juice. This intake undoubtedly plays some role in the perpetuation of the diarrhea because these juices contain enough poorly absorbed carbohydrate, such as sorbitol or fructose, to induce colonic
fermentation, resulting in the stimulus for diarrhea, as seen in other forms of carbohydrate intolerance.

A low dietary fat intake has been hypothesized to play a role in the persistence of the diarrhea, but this observation has not held up under scrutiny. However, because many of these children eventually are placed on strict elimination diets, dietary restriction of fiber and other residue may help perpetuate the loose stools.

One group of investigators has suggested that disordered small-intestine motility plays a role in chronic nonspecific diarrhea of childhood. They showed that the migrating motor complex of the duodenum was not suppressed as it normally should be with the introduction of glucose into the bowel, which implies that children with this disorder have relative hypermotility of the intestine during meals.

The diagnosis of chronic nonspecific diarrhea of childhood should be suspected if the following criteria are met: child’s age is between 6 and 36 months; two or more loose, voluminous stools, frequently containing undigested food particles, are passed per day; the diarrhea lasts for more than 4 weeks; abdominal pain is absent; failure to thrive is absent; and no definable cause is found for the chronic diarrhea (Box 344.1).